Happyly

Improvements
* Added `happyly.DUMMY_HANDLER` which returns back given message
([identity function](https://en.wikipedia.org/wiki/Identity_function))
* Dummy handler is default handler of all Executors

So you can simply provide message attributes to `run()`:

GoogleSimpleSender(
output_schema=MySchema(),
to_topic='happyly_testing',
project=os.environ['PROJECT'],
).run(
{'request_id': 'spam', 'label': 'eggs'}
)

Added
* `happyly.Schema` is now recommended instead of `marshmallow.Schema`. Define schema the same way as before by inheriting `happyly.Schema` and instantiate it simply with

my_schema = MySchema()

this will be strict by default and validating for unknown attributes automatically.
* Imports are now easier! Try `from happyly import Executor, Handler, Cacher` and more!

Incompatible changes
* `happyly.google_pubsub.GoogleCachedReceiveAndReply` and `happyly.google_pubsub.GoogleCachedReceiver` now require `from_topic` as obligatory argument. Obviously, this will make resending of cached messages a lot easier.

Added
* Caching: abstract and Redis-based.
* New high-level components for Google Pub/Sub with Redis caching out-of-the-box.

Changed
* All callbacks in Executor and Listener base classes are empty.

Documentation and type hints fixes

First release